The rapid expansion in volume of traffic carried over communications networks, in the form both of voice and other data signals, has resulted in continuing developments in communications hardware (e.g. optical systems carrying multiple wavelength signals at increasing symbol rates) and software (e.g. new systems and protocols such as GPRS, 3G mobile telephony, IPv6 and Mobile IP). The commercial needs to provide reliable, high quality communications services as cost-effectively as possible have resulted in the widespread incorporation in communications networks of devices for monitoring a wide variety of operational parameters. These parameters include basic indicators of proper functioning, such as bit error rate and jitter, as well as indicators of more user-oriented quality of service.
As new developments in hardware and software are incorporated into service-providing networks, the monitoring systems must likewise be updated. Design of monitoring and measurement tools for communication networks has to contend with two challenges: the very wide scope of the information to be measured, and changes and developments in the required types of measurement. Developing and producing tools that can measure ‘everything’, whether simultaneously or separately is a costly, long and arduous task. For example, current measuring instruments and monitoring probes must be pre-programmed with all of the measurements they are likely to need during their operational lifetime (to the extent these can practicably be foreseen). However, during typical use a particular user will often require only one or two key measurements from the suite provided by the equipment. Much of the measurement functionality will therefore lie dormant and unused. The list of protocols that must be supported by measurement systems is large and constantly increasing, and the number of applications and types of events that occur and must be monitored within communication networks is also very fluid. As a consequence, measurement and monitoring systems can quickly become out of date and require modification and modernization at an alarming rate.
A system that has the potential to support a variety of measurements for a large disparate customer base using many different protocols will require a great deal of code storage and therefore by its very nature be expensive to produce. A high level of flexibility is valuable in providing lower-cost targeted measurements. Measurement solutions based primarily on software controlling commodity hardware, such as standard general-purpose personal computers (PCs), can provide a highly flexible design. Typically some form of filtering is performed (e.g. by dedicated programs that run at a low level within the operating system of the device) on network traffic captured via a network interface. The filtered data are passed to measurement software modules running at higher levels of the operating system. New protocols and measurements can easily be added through software upgrades. It is also possible to store large suites of measurements on the main storage (e.g. magnetic hard disk) of such a device.
Unfortunately although commodity hardware is highly flexible it typically does not provide the performance required to monitor the very high (multi-gigabits per second) line speeds of current and emerging communication link technologies. Nor is commodity hardware compact, easily deployed, power efficient and cheap enough to be ubiquitous.
Conversely, a dedicated hardware-only solution typically has sufficient performance to measure high-speed links, but generally lacks flexibility. Hardware-based solutions are very difficult to change after they have been manufactured. At the very least such hardware must generally be returned to the factory or a service outlet for upgrading and installation of new protocols or additional measurements.
Hybrid approaches attempt to resolve this dilemma by selecting the most appropriate hardware and software components for the task at hand. However, these tend to be even more costly. A solution that contains the best software and hardware options is inherently less cost-effective. This hybrid approach also suffers the same constraints as predominantly software-based systems, i.e. power inefficiency, cost, heat dissipation and large physical size.
Most existing measuring and monitoring solutions provide a wide range of of real-time measurement features. But owing to space, size, and cost implications, few users can afford to have many of them placed at all the points where they consider it likely that their functions may be needed. To make best use of limited resource the devices must therefore be transported around the network as required.
A solution is highly desirable that delivers the optimum amount of measurement capability to perform the particular analysis the user desires, on the specific data the user wishes to analyze, just when the user requires it, without sacrificing functionality. Flexibility therefore continues to be of paramount importance. However, measurement systems will, by necessity, become more hardware oriented: recent massive increases in link speeds make this inevitable. Dedicated hardware offers the opportunity to re-design probes so that costs, scale, data rate and heat dissipation issues can be addressed.
Partly as a result, it is very likely that measurement and monitoring functionality will be incorporated into network elements such as routers, switches, servers, DSL/ADSL/cable modems, firewall units, private branch exchanges (PBXs) and media gateways. One example that has already been proposed by Agilent Technologies, Inc. involves incorporating measurement functionality in a router's line cards—see European patent application EP 1 152 570. Embedding measurement functionality in network equipment has the added advantage that measurements can become pervasive: anywhere and at anytime. The associated devices have a small physical footprint, consume little power and could be relatively inexpensive. This presents a very powerful set of features that could make large-scale measurement of the operation of systems such as the Internet a realistic possibility.
Unfortunately, even with rapid advances in hardware design, embedded devices are unlikely to have spare storage capacity to be pre-programmed with a large variety of measurements to suit many purposes. The cost effective utilization of the limited resources possessed by an embedded device is therefore critical. Furthermore, as new protocols and applications are developed a mechanism to upgrade the embedded devices without removing them from service (e.g. to be taken back to the factory or to a service point) will be highly desirable. Network operators and users are unlikely to tolerate a lengthy loss of service whilst units are sent away to be upgraded. Some of these issues could in principle be addressed by on-site servicing or ‘hot-swapping’ of the network elements in which the measurement and monitoring devices are embedded. However, this still entails loss of service and extra support costs or the purchase of extra sets of network element devices to swap in and send to be upgraded.
In summary, embedded devices are ideal for large-scale, cost-effective measurement solutions, such as described in EP 1 152 570. Moreover, the embedding of measurement devices into routers is likely to be just a beginning; conceivably all network elements could eventually contain similar functionality. Unfortunately the utility of embedded devices will be severely limited without the ability to add new measurements, support new protocols and maximize the limited storage resources of those devices.